This invention relates to the art of treating metals, metal alloys and metal oxides, and more particularly to a new and improved method for enhancing the electrical conductivity of metals, metal alloys and metal oxides.
One area of use of the present invention is in the manufacturing of electrodes for capacitors, batteries and the like, although the principles of the present invention can be variously applied. Metals and metal alloys have a native oxide present on the surface. This is an insulating layer and hence if the material is to be used as a substrate for an electrode, the oxide has to be removed or made electrically conductive.
If the oxide is removed by chemical treatment, such as by etching with an acid or electrolytic etching to expose the underlying metal, special steps must be taken in order to complete the electrical contacts before the native oxide can be regenerated and interfere with the electrical contacts. Such measures require special apparatus and extremely careful handling of the materials, all of which adds cost to the fabricating of electrical devices incorporating these materials to which electrical contact must be made. Another approach involves removing the oxide layer and plating the bare substrate metal with an expensive noble metal, such as silver, gold, or alloys of silver, gold and platinum, or the formation of an electrically conducting compound on the bare substrate surface. The materials employed are expensive and the steps required to plate the substrate are costly and time consuming. In addition, the metal plating or electrically conducting compound must be disposed on the substrate as a continuous film for maximum performance. Therefore, the plating or compound formation typically is carried out after the substrate metal is formed into its final shape for the electrical device in which it is incorporated in order to avoid damage to the coating. This, in turn, adds to the cost and complexity of the manufacturing process.
U.S. Pat. No. 5,098,485 issued Mar. 24, 1992 to David A. Evans proposes a solution to the oxide problem by altering the native oxide from an electrically insulating to an electrically conducting condition without removal of the native oxide layer to expose the underlying metal or alloy. A solution containing ions of an electrical material is applied to the native oxide layer, and then the substrate, oxide and applied ions are heated to an elevated temperature for a time sufficient to incorporate the ions into the oxide layer to change it from an electrical insulator to an electrical conductor.